The present invention relates to image forming apparatuses such as electrophotographic copying machines and printers. More particularly, the present invention is directed to an image forming apparatus having image data carrying members such as a photoreceptor, a transfer material carrying member, and an intermediate transfer body for carrying and forwarding image data rendered visible by a developer as well as high voltage requiring devices such as dischargers and chargers and contained in a unit that can be separated from the body of the image forming apparatus.
Conventional image forming apparatuses such as electrophotographic copying machines and printers use a transfer unit that is separable from the image forming apparatus body. Such a transfer unit contains: image data carrying members such as a photoreceptor, a transfer material carrying member, and an intermediate transfer body for carrying and forwarding image data rendered visible by a developer; devices such as a transfer corotron and adhesion corotron that require high voltage; and the like. A high voltage generating power supply for these high voltage requiring devices is usually disposed on the image forming apparatus body side and is connected to these devices through a high power cable and several junction connectors. However, this type of arrangement often requires that signal lines and the like run adjacent to the high power lines, and in this case, noise infiltrates into the signal lines from the high power lines, often causing erroneous operation.
To overcome this problem, a solution is disclosed in Japanese Patent Unexamined Publication No. 62-187371. According to this solution, a high voltage generating power supply is disposed within the transfer unit, so that the high voltage cable and junction connectors connected to the image forming apparatus body side can be eliminated to thereby prevent such noise-induced erroneous operation.
However, while there is no description in Japanese Patent Unexamined Publication No. 62-187371, it has been found out that desired current is not provided due to current leak at the high voltage line and junction connectors and that this impairs the image quality. In addition, if the transfer unit employs an endless belt, by only arranging a high voltage generating power supply inside the loop of the endless belt, a sufficient distance between the endless belt and the high voltage generating power supply cannot be provided due to the design restriction that a large thicknesswise space is not usually provided for the endless belt unlike the transfer drum. As a result, various problems are encountered.